The invention relates to a module for optical signal transmission, and to a transmitting and/or receiving apparatus having such a module.
Modules for bidirectional optical data traffic operate, for example, using a star structure in such a way that data streams are transmitted in opposite directionsxe2x80x94in the direction to a central feed point (upstream) and in the direction to further receivers (downstream) in an optical fiber. Identical or different wavelengths can thereby be used for the individual data channels. There is a need to achieve ever higher data rates, with the costs decreasing. Wavelength-division multiplexing methods are used in particular for this purpose wherein light signals at a number of wavelengths are transmitted simultaneously on one optical fiber.
In this case, it is necessary to separate the light signals which are at a number of wavelengths in the receiver once again. In addition, it should be possible to transmit optical signals from the receiver in the direction of the feed point. There is thus a need for electrooptical modules with a number of optical ports.
U.S. Pat. No. 4,767,171 (see European patent application EP 238 977) discloses a transmitting and receiving module for a bidirectional communications network having free-beam optics, wherein spherical lenses are arranged at a distance from one another between a laser diode and the end of an optical fiber, and focus the laser light onto the end of the fiber. A wavelength-selective beam splitter is arranged between the spherical lenses for wavelength separation and separates from the beam path light which is transmitted from the light fiber end and is at a wavelength other than the wavelength of the laser light, and supplies this light to a detector or receiving component.
A disadvantage of that prior art module is that a number of highly complex assembly steps are required successively, each of which involves the use of substantial resources. If one assembly step in the process is unsuccessful, the previous assembly steps must also be rejected.
The object of the present invention is to provide a module for optical signal transmission which overcomes the above-noted deficiencies and disadvantages of the prior art devices and methods of this general kind, and which provides for a transceiver for at least two data channels, which has a simple, compact modular design and which can be produced cost-effectively.
With the above and other objects in view there is provided, in accordance with the invention, a module for optical signal transmission, comprising:
a carrier;
at least one transmitting or receiving component mounted on the carrier;
at least one optical waveguide having an optical axis, a first end representing an optical input of the module, and a second end representing an optical output of the module; and
a wavelength-selective element disposed in the optical waveguide and configured to couple light of a specific optical data channel from the optical waveguide to the transmitting or receiving component or inject into the optical waveguide light emitted from the transmitting or receiving element;
whereby the light is injected into or coupled out of the optical waveguide substantially perpendicular to the optical axis of the optical waveguide.
In other words, the object of the invention is to provide at least one optical waveguide in the module, the two ends of which optical waveguide represent an optical input and an optical output of the module, and each of which has an associated transmitting or receiving component. A wavelength-selective element is arranged or formed in the optical waveguide and injects into the optical waveguide, or outputs from it, light, which is emitted from or received by a transmitting or receiving element for a specific optical data channel, without influencing the other data channels. Light is in this case injected into or output from the optical waveguide, essentially at right angles to the optical axis of the optical waveguide.
The expression xe2x80x9csubstantially perpendicularxe2x80x9d in this case means that the angle is such that light which falls on the wavelength-selective element is allowed to be deflected into the optical waveguide and vice versa.
The solution according to the invention provides a design concept which is based on the use of a type of optical xe2x80x9cT-elementxe2x80x9d, wherein the horizontal xe2x80x9cT-barxe2x80x9d is provided by a continuous optical waveguide. Light is output from and injected into the optical waveguide between the optical input and output essentially at right angles to the optical axis of the optical waveguide. The interfaces of this module are two optical interfaces at the two ends of the optical waveguide and an electrical interface for making electrical contact between the transmitting or receiving component, and, in particular, a printed circuit board.
The optical module can be cascaded, and a transmitting and/or receiving device according to the invention accordingly has a number of modules which are arranged one behind the other. The fact that the individual modules can be combined as required, means that, depending on the application, it is possible to provide multiplexes and/or demultiplexes in principle for any desired number of data channels, with light at one wavelength being injected or output in each module. The combination options for the individual modules or xe2x80x9cT-elementsxe2x80x9d also allow the data rates to be upgraded or provided retrospectively on a customer-specific basis.
A further advantage of the invention is that the individual modules can involve the use of very few resources and can be produced cost-effectively. A faulty module can be replaced on its own and does not affect the functionality of a transmitting and/or receiving device.
In accordance with an added feature of the invention, the at least one optical waveguide is arranged in or on an optical waveguide body which is mounted on the carrier for the transmitting or receiving component. This results in the module having a compact arrangement. Encapsulation against external influences is also provided.
The module according to the invention can advantageously be connected by being plugged to further modules. To this end, the optical waveguide body preferably has holes via which the optical waveguide body can be connected to further optical waveguide bodies of further modules by means of centering pins. In this way, a number of modules according to the invention can easily be plugged together to form a desired transmitting and/or receiving device.
In accordance with an additional feature of the invention, the wavelength-selective element is a wavelength-selective mirror which is arranged in the optical waveguide or is formed by it. For example, the wavelength-selective mirror is formed on a push-in element which is pushed into the optical waveguide body, preferably at an angle of approximately 45xc2x0, and in the process interrupts the optical waveguide.
It is likewise within the scope of the invention to provide the wavelength-selective element by the optical waveguide forming two optical waveguide sections each having at least one inclined end surface with the optical waveguide sections being joined together axially at the inclined end surfaces. One of the abutting end surfaces of the optical waveguide sections is in this case coated with a wavelength-selective filter, with light being injected into or output from the optical waveguide for a specific optical data channel by the light for the optical data channel being passed to, or emerging from the inclined end surface at an angle to the optical axis of the optical waveguide.
In a further embodiment of the wavelength-selective element, the wavelength-selective element is formed by a Fiber-Bragg grating, which runs obliquely in the optical waveguide. In this case, a periodic refractive index change is produced in the optical waveguide by additional laser beams, in particular two crossing lasers, which results in a grating structure on which light is output or injected on a wavelength-selective basis.
A further possibility for providing a wavelength-selective element is to fit a notch in the waveguide, which notch is provided with a wavelength-selective coating.
In one preferred refinement of the module, the carrier for the transmitting or receiving component has a housing on which the optical waveguide body is mounted. This provides reliable protection against external influences. The carrier preferably and furthermore has a connecting contact for making electrical contact between the transmitting or receiving component and a printed circuit board which is formed, for example, by a lead frame.
The optical waveguide which is arranged in the waveguide body is, in one embodiment, an integrated optical conductor, for example, using glass on silicon technology. However, it is also possible for the optical waveguide to be an optical fiber, in particular a single-mode fiber, with the waveguide body being composed, for example, of a plastic.
It is within the scope of the invention for a number of optical waveguides to be arranged parallel to one another in the optical waveguide body, with each optical waveguide having a respective associated transmitting or receiving component so that the module can also be connected to an optical waveguide array.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in module for optical signal transmission, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.